Treatment of Cancer Involving Mutated KRAS or BRAF Genes

ABSTRACT

The present invention provides a method of treating cancer in a subject wherein the cancer comprises mutated KRAS or BRAF genes. The method comprises administering to the subject an effective amount of an antibody or antigen binding fragment thereof wherein the antibody or antigen binding fragment thereof competes with SC104 for binding to the human colon cancer cell line Colo205.

This application is associated with and claims priority from U.S. patent application No. 61/258,518 filed on 5 Nov. 2009 and Australian patent application no. 2010904107 filed on 13 Sep. 2010, the entire contents of each of these applications are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to methods of treating cancer in a subject wherein the cancer comprises mutated KRAS or BRAF genes. The method involves the administration of an antibody or antigen binding fragment thereof to the subject. The present invention also relates to methods of treatment of cancer which involve the determination of the KRAS or BRAF status of the patient.

BACKGROUND

Carbohydrate structures can be tumour-specific or tumour-associated antigens and are thus the focus of many antibody-generating immunization strategies. However, generating anti-carbohydrate specific antibodies is a challenging task as they may lack specificity, affinity or are only of the IgM class (Christensen et al., 2009). Moreover, generating humanised anti-carbohydrate antibodies that have the capacity to kill cancer cells is a challenging task, a fact that is reflected in the rare number of reports on such antibodies. There is only one example of an anti-glycolipid antibody that has been successfully humanised; the antibody recognises the ganglioside GM2 and kills human tumour cells in vitro and in vivo (U.S. Pat. Nos. 6,423,511 and 6,872,392). Although not humanised there are two other examples of carbohydrate-binding antibodies that have been engineered for human administration. Firstly, anti-carbohydrate antibody RAV-12 is a chimeric mouse-human IgG₁ that shows in vitro and in vivo efficacy against human colon cancer cells (Loo et al., 2007). Secondly, anti-carbohydrate antibody HMMC-1 has shown in vitro efficacy against human ovarian cancer. HMMC-I is a fully human antibody generated by transchromosomal KM mice (Nozawa et al., 2004).

International patent application No. WO 2005/108430 discloses an anti-cancer mouse monoclonal antibody which is designated SC104. The CDR sequences of this antibody are set out in Table 1. The disclosure of this application is incorporated herein by reference. The exact nature of antigen to which SC104 binds is unclear but WO2005/108430 suggests that the antigen is a sialyltetraosyl carbohydrate. It is also disclosed that SC104 is capable of directly inducing cell death without the need for immune effector cells. As described in co-pending international patent application No. WO 2010/105290 a number of humanised versions of SC104 have been developed. The disclosure of this application is also incorporated herein by reference.

The therapeutic treatment of human cancers is challenging and can, in some cases, be enhanced by correlating molecular biomarkers with treatment outcome. For example mutations in the genes KRAS (alternatively named ki-ras or k-ras) or BRAF give rise to proteins with altered signalling properties in the tumour cells. Mutations in these biomarkers are known to correlate with unsuccessful outcomes in cancer treatment that use therapeutic antibodies targeting the epidermal growth factor receptor, for example cetuximab or panitumumab (Amado, Wolf et al. 2008; Karapetis, Khambata-Ford et al. 2008; Di Nicolantonio, Martini et al. 2008; Loupakis, Ruzzo et al. 2009; Lievre, Bachet et al. 2006). The KRAS mutations are of particular medical significance as they occur in 35%-45% of colorectal cancer patients; BRAF mutations occur in less than 15% (Siena, Sartore-Bianchi et al. 2009). Furthermore, KRAS mutations are found in 70%-95% of pancreatic carcinoma tissues (Saif et al. 2007).

SUMMARY OF THE INVENTION

In a first aspect the present invention provides a method of treating cancer in a subject wherein the cancer comprises mutated KRAS or BRAF genes, the method comprising administering to the subject an effective amount of an antibody or antigen binding fragment thereof wherein the antibody or antigen binding fragment thereof competes with SC104 for binding to the human colon cancer cell line Colo205.

In a second aspect the present invention provides a method of treating cancer in a subject, the method comprising testing the cancer for the presence of mutated KRAS or BRAF genes and administering to subjects in which the cancer comprises mutated KRAS or BRAF genes an effective amount of an antibody or antigen binding fragment thereof wherein the antibody or antigen binding fragment thereof competes with SC104 for binding to the human colon cancer cell line Colo205.

In a third aspect the present invention provides use of an antibody or antigen binding fragment thereof which competes with SC104 for binding to the human colon cancer cell line Colo205 in the preparation of a medicament for the treatment of cancer in a subject wherein the cancer comprises mutated KRAS or BRAF genes.

In a fourth aspect the present invention provides an antibody or antigen binding fragment thereof which competes with SC104 for binding to the human colon cancer cell line Colo205 in the treatment of cancer in a subject wherein the cancer comprises mutated KRAS or BRAF genes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1—Humanised SC104 antibody (SEQ ID NO:7/SEQ ID NO:50) binds to human gastrointestinal cancer with mutated and wild-type KRAS genes. Shown in FIG. 1 are individual and mean immunohistochemistry binding intensity to a panel of donor tumour samples (n=number of donors); there was no statistical significant difference in staining intensity between the wild-type or mutated groups of each respective tumour type as determined by a Mann-Whitney test.

FIG. 2—Humanised SC104 antibody (SEQ ID NO:7/SEQ ID NO:94) binds to human colon cancer cells with mutated and wild-type KRAS genes, as determined by immunohistochemistry.

FIG. 3—Humanised SC104 antibody variants incorporating the 1U6A framework (VL/VH SEQ ID NO:7/SEQ ID NO:50 and SEQ ID NO:7/SEQ ID NO:25) and humanised SC104 antibody variants incorporating the 1QLR framework (VL/VH SEQ ID NO:8/SEQ ID NO:38 and SEQ ID NO:8/SEQ ID NO:26) have potent antibody-dependent cell-mediated cytotoxicity as determined by LDH release assays using the SC104 antigen positive human colon cancer cell line C170. The chimeric SC104 antibody (SEQ ID NO:4/SEQ ID NO:2) is shown as a comparator and the human IgG1 isotype is used as a negative control. Each point represents mean±SD of three replicate samples.

FIG. 4—Humanised SC104 antibody variants incorporating the 1U6A framework (VL/VH SEQ ID NO:7/SEQ ID NO:50 and SEQ ID NO:7/SEQ ID NO:25) and humanised SC104 antibody variants incorporating the 1QLR framework (VL/VH SEQ ID NO:8/SEQ ID NO:38 and SEQ ID NO:8/SEQ ID NO:26) have potent complement-dependent cytotoxicity as determined by cell viability assays using the SC104 antigen positive human colon cancer cell line Colo205. The chimeric SC104 antibody (SEQ ID NO:4/SEQ ID NO:2) is shown as a comparator along with a human IgG1 isotype negative control. Each point represents mean±SD of three replicate samples.

FIG. 5—Humanised SC104 antibody (SEQ ID NO:7/SEQ ID NO:50) has potent antibody-dependent cell-mediated cytotoxicity against human colon cancer cell line DLD-1 (KRAS mutated) as assessed by LDH release assays. The human IgG1 isotype is used as a negative control. Each point represents mean±SD of three replicate samples.

FIG. 6—Humanised SC104 antibody (SEQ ID NO:7/SEQ ID NO:50) has potent antibody-dependent cell-mediated cytotoxicity against human colon cancer cell lines Colo201 (A), Colo205 (B), WiDr (C) and HT-29 (BRAF mutated) (D) as assessed by LDH release assays. The human IgG1 isotype is used as a negative control for Colo201. Each point represents mean±SD of three replicate samples.

FIG. 7—Kifunensin-treated humanised SC104 antibody (SEQ ID NO:7/SEQ ID NO:50) has higher antibody-dependent cell-mediated cytotoxicity compared with untreated antibody as assessed by LDH release assays using the SC104 antigen positive WiDr human colon cancer cell lines. Each point represents mean±SD of three replicate samples.

FIG. 8—Treatment of HT29 xenograft tumour-bearing mice with humanised SC104 antibody (SEQ ID NO:7/SEQ ID NO:50) leads to significant, reduced tumour burden compared with vehicle control treatment. A: mean±SEM tumour volume in groups of 6-10 mice. Asterisks indicate significant differences between treatment groups, p<0.05 Mann-Whitney test. B: mean and individual tumour weight at end of study. P value as determined by Mann-Whitney test

FIG. 9—Competitor antibody (SEQ ID NO:7/SEQ ID NO:50 (-▴-)), but not human isotype control antibody (-o-), markedly reduces binding of fluorescent-labelled mouse SC104 antibody (A—1 ug/ml; B—10 ug/ml) as assessed by flow cytometry using the antigen positive cell line Colo205.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to methods of treating cancer in which the cancer comprises mutations in either KRAS or BRAF genes. The method involves the use of antibodies or antigen binding fragments thereof which compete with SC104 for binding to the human colon cancer cell line Colo205. In various embodiments the invention involves the use of SC104, SC104 chimaeras, humanised SC104, deimmunised SC104 or antigen binding fragments thereof in the treatment of cancer wherein the cancer comprises mutations in either KRAS or BRAF genes. It is preferred that the antibody is not SC104.

In a first aspect the present invention provides a method of treating cancer in a subject wherein the cancer comprises mutated KRAS or BRAF genes, the method comprising administering to the subject an effective amount of an antibody or antigen binding fragment thereof wherein the antibody or antigen binding fragment thereof competes with SC104 for binding to the human colon cancer cell line Colo205.

In a second aspect the present invention provides a method of treating cancer in a subject, the method comprising testing the cancer for the presence of mutated KRAS or BRAF genes and administering to subjects in which the cancer comprises mutated KRAS or BRAF genes an effective amount of an antibody or antigen binding fragment thereof wherein the antibody or antigen binding fragment thereof competes with SC104 for binding to the human colon cancer cell line Colo205.

In a third aspect the present invention provides use of an antibody or antigen binding fragment thereof which competes with SC104 for binding to the human colon cancer cell line Colo205 in the preparation of a medicament for the treatment of cancer in a subject wherein the cancer comprises mutated KRAS or BRAF genes.

In a fourth aspect the present invention provides an antibody or antigen binding fragment thereof which competes with SC104 for binding to the human colon cancer cell line Colo205 in the treatment of cancer in a subject wherein the cancer comprises mutated KRAS or BRAF genes.

As used herein “competes” means that the antibody or antigen binding fragment thereof when used at the same concentration as SC104 reduces the binding of SC104 to the human colon cancer cell line Colo205 by at least 10%. The level of binding of SC104 to Colo205 may be assessed in a flow cytometry-based binding assay known to those skilled in the art. In such an assay the binding signal of fluorochrome-labelled SC104 antibody to Colo205 is measured in the presence of various dilutions of competitor antibody. Fluorochrome labelling of SC104 could be achieved by direct conjugation or by indirect detection methods such as SC104 biotin/streptavidin-fluorochrome or fluorochrome-conjugated secondary antibody that detects SC104 but not competitor antibody.

As will be appreciated it is preferred that the KRAS and/or BRAF status of the cancer is determined prior to therapy. Methods of determining whether cells comprise mutated KRAS or BRAF genes are well known in the art. These methods include those described in (Lievre, Bachet et al. 2006) and (Seth, Crook et al. 2009).

In various forms of the invention the antibody is mouse SC104 (variable regions listed in SEQ ID NO:3/SEQ ID NO:1) or SC104 chimera. As will be understood a chimera is an antibody in which the murine constant region has been replaced with a human or primate constant region. An example of such a chimera is shown in SEQ ID NO:4/SEQ ID NO:2. As mentioned above it is preferred that the antibody is not SC104 in order to avoid a Human Anti Mouse Antibody (HAMA) response in humans.

In other forms of the invention the antibody is a deimmunised version of SC104 or an antigen binding fragment thereof. The deimmunisation of antibodies is a methodology well understood in the art. For example reduction of the immunogenicity of antibodies such as murine antibodies by deimmunisation is described in WO 00/34317, WO 98/52976, WO 02/079415, WO 02/012899 and WO 02/069232 (the disclosures of which are incorporated herein by cross reference). In general, deimmunisation entails carrying out substitutions of amino acids within potential T cell epitopes. In this way, the likelihood that a given sequence will give rise to T cell epitopes upon intracellular protein processing is reduced. Moreover, WO 92/10755 describes an approach in which antigenic determinants on proteins are engineered. Particularly, proteins are epitope mapped and their amino acid sequence is changed through genetic engineering.

In other embodiments the antibody is a humanised version of SC104. In general, humanisation entails substitutions of non-human antibody sequences for corresponding human sequences, as for example is the case with CDR-grafting. Examples of this approach are described in WO 91/09968 and U.S. Pat. No. 6,407,213. As mentioned above, a number of humanised versions of SC104 have been developed which compete with SC104 for binding to the human colon cancer cell line Colo205. These humanised antibodies are described in co-pending international patent application No. WO 2010/105290.

In this regard in an embodiment of the present invention the antibody or antigen binding fragment thereof comprises at least one sequence selected from the group consisting of SEQ ID NO:7, SEQ ID NO:8, SEQ ID NO:11, SEQ ID NO:12, SEQ ID NO:13, SEQ ID NO:14, SEQ ID NO:15, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:19, SEQ ID NO:20, SEQ ID NO:21, SEQ ID NO:22, SEQ ID NO:23, SEQ ID NO:24, SEQ ID NO:25, SEQ ID NO:26, SEQ ID NO:27, SEQ ID NO:28, SEQ ID NO:29, SEQ ID NO:30, SEQ ID NO:31, SEQ ID NO:32, SEQ ID NO:33, SEQ ID NO:34, SEQ ID NO:35, SEQ ID NO:36, SEQ ID NO:37, SEQ ID NO:38, SEQ ID NO:39, SEQ ID NO:40, SEQ ID NO:41, SEQ ID NO:42, SEQ ID NO:43, SEQ ID NO:44, SEQ ID NO:45, SEQ ID NO:46, SEQ ID NO:47, SEQ ID NO:48, SEQ ID NO:49, SEQ ID NO:50, SEQ ID NO:51, SEQ ID NO:52, SEQ ID NO:53, SEQ ID NO:62, SEQ ID NO:69, SEQ ID NO:70, SEQ ID NO:73, SEQ ID NO:74, SEQ ID NO:75, SEQ ID NO:76, SEQ ID NO:77, SEQ ID NO:78, SEQ ID NO:79, SEQ ID NO:80, SEQ ID NO:81, SEQ ID NO:82, SEQ ID NO:83, SEQ ID NO:84, SEQ ID NO:85, SEQ ID NO:86, SEQ ID NO:87, SEQ ID NO:88, SEQ ID NO:89, SEQ ID NO:90, SEQ ID NO:91, and SEQ ID NO:94

In a further preferred embodiment of the antibody or antigen binding fragment thereof comprises light and heavy chain combinations selected from the group consisting of SEQ ID NO:7/SEQ ID NO:25, SEQ ID NO:7/SEQ ID NO:50, SEQ ID NO:7/SEQ ID NO:94, SEQ ID NO:8/SEQ ID NO:26 and SEQ ID NO:8/SEQ ID NO:38.

As will be appreciated the sequences described in the present invention may be modified using methods well known in the art to increase binding, by for example, affinity maturation, or to decrease immunogenicity by removing predicted MHC class II-binding motifs. The therapeutic utility of the sequences developed and described herein can be further enhanced by modulating their functional characteristics, such as antibody-dependent cell-mediated cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC), serum half-life, biodistribution and binding to Fc receptors or the combination of any of these. This modulation can be achieved by protein-engineering, glyco-engineering or chemical methods. Depending on the therapeutic application required, it could be advantageous to either increase or decrease any of these activities.

An example of glyco-engineering used the Potelligent® method as described in Shinkawa T. et al., 2003 (J Biol Chem 278: 3466-73). The variable light and heavy chain regions of the humanised antibody variants were expressed as an IgG1 on a standard constant region backbone. The sequence of the constant heavy chain was GenBank accession number P01857.1 and the sequence of the constant light chain was NCBI accession number P01834.

Numerous methods for affinity maturation of antibodies are known in the art. Many of these are based on the general strategy of generating panels or libraries of variant proteins by mutagenesis followed by selection and/or screening for improved affinity. Mutagenesis is often performed at the DNA level, for example by error prone PCR (Thie, Voedisch et al. 2009), by gene shuffling (Kolkman and Stemmer 2001), by use of mutagenic chemicals or irradiation, by use of ‘mutator’ strains with error prone replication machinery (Greener 1996) or by somatic hypermutation approaches that harness natural affinity maturation machinery (Peled, Kuang et al. 2008). Mutagenesis can also be performed at the RNA level, for example by use of Qβ replicase (Kopsidas, Roberts et al. 2006). Library-based methods allowing screening for improved variant proteins can be based on various display technologies such as phage, yeast, ribosome, bacterial or mammalian cells, and are well known in the art (Benhar 2007). Affinity maturation can be achieved by more directed/predictive methods for example by site-directed mutagenesis or gene synthesis guided by findings from 3D protein modeling (see for example Queen, Schneider et al. 1989 or U.S. Pat. No. 6,180,370 or U.S. Pat. No. 5,225,539).

Methods of increasing ADCC have been described by Ferrara, Brunker et al. 2006; Li, Sethuraman et al. 2006; Stavenhagen, Gorlatov et al. 2007; Shields, Namenuk et al. 2001; Shinkawa, Nakamura et al. 2003; and WO 2008/006554.

Methods of increasing CDC have been described by Idusogie, Wong et al. 2001; Dall'Acqua, Cook et al. 2006; Michaelsen, Aase et al. 1990; Brekke, Bremnes et al. 1993; Tan, Shopes et al. 1990; and Norderhaug, Brekke et al. 1991.

References describing methods of increasing ADCC and CDC include Natsume, In et al. 2008. The disclosure of each of these references is included herein by cross reference.

A number of methods for modulating antibody serum half-life and biodistribution are based on modifying the interaction between antibody and the neonatal Fc receptor (FcRn), a receptor with a key role in protecting IgG from catabolism, and maintaining high serum antibody concentration. Dall'Acqua et al describe substitutions in the Fc region of IgG1 that enhance binding affinity to FcRn, thereby increasing serum half-life (Dall'Acqua, Woods et al. 2002) and further demonstrate enhanced bioavailability and modulation of ADCC activity with triple substitution of M252Y/S254T/T256E (Dall'Acqua, Kiener et al. 2006). See also U.S. Pat. Nos 6,277,375; 6,821,505; and 7,083,784. Hinton et al have described constant domain amino acid substitutions at positions 250 and 428 that confer increased in vivo half-life (Hinton, Johlfs et al. 2004). (Hinton, Xiong et al. 2006). See also U.S. Pat. No 7,217,797. Petkova et al have described constant domain amino acid substitutions at positions 307, 380 and 434 that confer increased in vivo half-life (Petkova, Akilesh et al. 2006). See also Shields et a12001 and WO 2000/42072. Other examples of constant domain amino acid substitutions which modulate binding to Fc receptors and subsequent function mediated by these receptors, including FcRn binding and serum half-life, are described in U.S. Pat. Application Nos 20090142340; 20090068175; and 20090092599.

The glycans linked to antibody molecules are known to influence interactions of antibody with Fc receptors and glycan receptors and thereby influence antibody activity, including serum half-life (Kaneko, Nimmerjahn et al. 2006; Jones, Papac et al. 2007; and Kanda, Yamada et al. 2007). Hence, certain glycoforms that modulate desired antibody activities can confer therapeutic advantage. Methods for generating engineered glycoforms are known in the art and include but are not limited to those described in U.S. Pat. Nos. 6,602,684; 7,326,681; 7,388,081; and WO 2008/006554.

Extension of half-life by addition of polyethylene glycol (PEG) has been widely used to extend the serum half-life of proteins, as reviewed, for example, by Fishburn 2008.

As will be recognised it is possible to make conservative amino acid substitutions within the sequences of the current invention. By “conservative substitution” is meant amino acids having similar properties. As used in this specification the following groups of amino acids are to be seen as conservative substitutions:

H, R and K; D,E,N and Q; V, I and L; C and M; S, T, P, A and G; and F, Y and W.

Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

All publications mentioned in this specification are herein incorporated by reference. Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed in Australia or elsewhere before the priority date of each claim of this application.

In order that the nature of the present invention may be better understood preferred forms thereof will now be described by reference to the following Examples.

Example 1 Immunohistochemistry Protocol

A multi-tumour human tissue microarray containing samples of a range of tumour types from different donors was screened for binding to biotinylated humanised SC104 antibody variants using immunohistochemistry. Biotinylated human IgG₁ isotype was used for negative control staining. Immunoreactivity by the antibody was graded by visual inspection in a four step scale based on staining intensity and percentage of positive cells.

Humanised SC104 Antibody Variant Binds to Various Human Cancer Types

A number of different cancer types from different human patients were analysed for binding with a humanised SC104 antibody (SEQ ID NO:7/SEQ ID NO:50). The humanised SC104 antibody, but not the human isotype control, bound to human colon cancer tissues demonstrating the specificity of the binding conditions used (data not shown). Table 2 summarises that positive membrane staining was found in colon cancer up to 75%. Surprisingly, high frequency positive staining was found in pancreatic cancer up to 95% and to a lower extent in other solid tumours. In contrast, no staining was observed for gastrointestinal stroma tumours. These results indicate that the humanised SC104 antibody is useful for tumour diagnosis in indications of colorectal, pancreatic, ovarian and lung malignancies. In addition, one can envisage that the humanised SC104 antibody is useful for the therapeutic treatment of colorectal, pancreatic, ovarian and lung cancer in humans. Such anti-tumour efficacy in vivo could be evaluated in mouse tumour xenograft models.

A further tissue microarray was constructed from primary human colon and gastric tumours that were passaged as xenotransplants in nude mice. Tumour samples were screened for binding to humanised SC104 antibody using an antibody precomplexing method and HRP visualisation. Humanised SC104 antibody was pre-complexed with an anti-human Fab-FITC, blocked with excess human IgG, and subsequently this complex was utilized as the primary antibody reagent that was incubated on the tissue microarray. For negative control staining humanised SC104 antibody was exchanged with a human IgG1 isotype control. Immunoreactivity by the antibody was graded by visual inspection in a five step scale: 0=no staining, 1=few staining spots, 2=solid positive staining, 3=>50% positive staining, 4=saturated staining. Staining data are represented as a mean of three sections and are shown in FIG. 1.

Analysis of KRAS Gene Status

Genomic DNA of primary human tumours passaged as mouse xenotransplants was analysed in exon 1 and exon 2 of the KRAS gene. Nucleotide sequencing analysis revealed if the exons encoded normal or activating mutations in the KRAS protein. The majority of the mutated KRAS samples were heterozygous.

Humanised SC104 antibody (SEQ ID NO:7/SEQ ID NO:50) binds to human gastrointestinal cancer tissue with mutated and normal KRAS gene status using immunohistochemistry analysis (FIG. 1).

The humanised and Potelligent®-engineered SC104 antibody (SEQ ID NO:7/SEQ ID NO:94) was also shown by histochemistry to bind human colon cancer cells with mutated or wild-type KRAS genes (FIG. 2).

Example 2 Flow Cytometry-Based Binding Assays

Viable tumour cells and control cells (2×10⁵, as determined by trypan blue exclusion) were incubated in triplicate with mouse SC104, chimeric SC104 or humanised variants, and human IgG₁ isotype (Sigma-Aldrich®) at various concentrations in 100 μl of buffer (PBS plus 1% FCS) in 96 V-well plates (Eppendorf) for 20 min on ice in the dark. Cells were washed twice with buffer before incubation for 20 min in 100 μl of buffer containing goat anti-human IgG (Fc-specific, Sigma-Aldrich®, conjugated to FITC) or goat anti-mouse IgG (Fc-specific, Sigma-Aldrich®, conjugated to FITC) for detecting chimeric or mouse antibodies, respectively. After washing, cells were resuspended in buffer and analysed for antibody binding by flow cytometry on a Cell Lab Quanta™ SC MPL (Beckman Coulter) using Electronic Volume (EV), side scatter and FL-1 gating; during acquisition the cells in the 96-well plate were cooled by underlying a cool pack (Eppendorf). Results were expressed as mean fluorescent intensity (MFI); curve slope values were calculated using non-linear regression analysis by GraphPad Prism® software.

Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC) Assay

Effector (peripheral blood mononuclear) cells were purified from Buffy Coat preparation of normal human donors (provided by Australian Red Cross Blood Services) using Lymphoprep™ according to the manufacturer's protocol (Axis-Shield PoC AS). Viable effector cells (5×10⁶/ml) were incubated overnight in RPMI 1640 (Gibco®) plus 10% FCS at 37° C. and 10% CO₂. Tumour target cells and effector cells were washed in PBS followed by media (RPMI1640 w/o phenol red, Gibco®, plus 0.5% FCS), resuspended in media and incubated with various concentrations of antibody (chimeric SC104, humanised SC104 or human IgG₁ isotype, Sigma-Aldrich®, # I5154) in triplicate in 96-well U well plates (Corning®) in a 200 μl assay consisting of the following final concentrations: target cells, 1×10⁵ cells/ml; effector cells, 2.5×10⁶ cells/ml; antibody range 10 to 0.001 ug/ml. For controls, target cells only were incubated in the absence (min target) or presence (max target) of 1% Triton®-X (Sigma-Aldrich®), and target and effector cells (background) were incubated in the absence of antibody. Plates were centrifuged for 2 min at 160 xg and incubated in hunified CO₂ atmosphere in 37° C. for 4 hours. Cell death was measured using a Lactate Dehydrogenase release assay. Briefly, plates were centrifuged for 5 min at 250 xg and 100 μl of cell supernatant was assayed for Lactate Dehydrogenase release using the Cytotoxicity Detection Kit (Roche) according to the manufacturer's guidelines. To minimise contaminating cell carry-over the supernatant was filtered through a 96-well 0.2 micron AcroPrep™ plate (Pall). LDH release was quantified by reading absorbance at 492 nm and percentage cytotoxicity was calculated using the following formula: 100×[sample−mean (background)]/mean (max target−min target); EC₅₀ values were calculated using non-linear regression analysis by GraphPad Prism® software.

Complement-Dependent Cytotoxicity (CDC) Assay

Viable tumour target cells were incubated in media (RPMI1640 w/o phenol red, Gibco®, plus 5% FCS), with human complement serum (Sigma-Aldrich® #S1764) and various concentrations of antibody (chimeric SC104, humanised SC104 or human IgG₁ isotype, Sigma-Aldrich®, # I5154) in triplicate in 96-well flat well plates (Corning®) in a 150 μl assay consisting of the following final concentrations: target cells, 13.3×10⁴ cells/ml; complement, 15%; antibody range 10 to 0.01 ug/ml. For controls, target cells only were incubated in the absence (target background) or presence (target & complement background) of complement, and complement (complement background) was incubated in media only. Plates were centrifuged for 2 min at 160×g and incubated in hunified CO₂ atmosphere in 37° C. for 2-3 hours. Cell death was measured using the CellTiter 96® kit (Promega®) according to the manufacturer's guidelines including an additional incubation period of 3-4 hours. Death of target cells was quantified by reading absorbance at 492 nm and percentage cytotoxicity was calculated using the following formula: 100×[sample−mean (target & complement background)]/[mean (complement background)−mean (target & complement background)]; EC₅₀ values were calculated using non-linear regression analysis by GraphPad Prism® software.

Novel Humanised SC104 Antibody Variants have Potent Cytotoxicity Against Human Colon Tumour Cells

Cytotoxicity against colon tumour cells of humanised SC104 variants was tested in antibody-dependent cell-mediated cytotoxicity and complement-dependent-cytotoxicity assays. The humanised SC104 antibody variants and the chimeric SC104 antibody, but not the human isotype control, had potent antibody-dependent cell-mediated cytotoxicity against C170 tumour cells using peripheral blood mononuclear cells of a normal human donor (FIG. 3). Similar results were obtained using peripheral blood mononuclear cells from other human donors (data not shown). FIG. 4 shows that the same panel of humanised SC104 antibody variants and the chimeric SC104 antibody, but not the human isotype control, had potent complement-dependent-cytotoxicity against Colo205 tumour cells using human complement. Binding and killing activities for the humanised SC104 antibody variants are summarized in Table 3.

Example 3 Flow Cytometry-Based Direct Killing Assays

Viable tumour cells (2×10⁵, as judged by trypan blue exclusion) were incubated in triplicate with mouse SC104, chimeric SC104 or humanised variants, and human IgG₁ isotype (Sigma-Aldrich®) at various concentrations in 80 μl of buffer (PBS plus 1% FCS) in 96 V-well plates (Eppendorf) for 2.5 to 3 hours at room temperature in the dark. To each well was added 0.15 g of 7AAD (BD® Biosciences) in 20 μl of buffer, and cells were incubated for further 20 min before cell viability was assayed by flow cytometry on a Cell Lab Quanta™ SC MPL (Beckman Coulter) using Electronic Volume (EV), side scatter and FL-3 gating; during acquisition the cells in the 96-well plate were cooled by underlying a cool pack (Eppendorf). Results were expressed as percentage of 7AAD⁺ cells; curve slope values were calculated using non-linear regression analysis by GraphPad Prism® software.

Binding and Killing Activity Against Human Pancreatic Cell Lines

Humanised and Potelligent®-engineered SC104 antibody (SEQ ID NO:7/SEQ ID NO:94) binds to and directly kills human pancreatic tumour cell lines with or without KRAS mutations as measured in flow cytometry assays.

Pancreatic Direct tumour KRAS Binding killing cell line status activity activity BxPC-3 Wild-type ++ + Su.86.86 Mutant +++ +++ Capan-2 Mutant ++ ++ CFPAC-1 Mutant + + Panc-1 Mutant − − Note: KRAS status described in Konishi et al., 2007 Cancer Research 67: 8460-8467 and Song et al., 2000 Neoplasia 2: 261-272. Activity is qualified as −, <0.1%; +, 0.1%-24%; ++, 25%-49%, +++, >50% positive cells.

Example 4 Human Colon Cancer Cell Lines Used for Assays

DLD-1 (ATCC accession number CCL-221; KRAS mutant; BRAF wild-type), Colo201 (ATCC accession number CCL-224; KRAS wild-type; BRAF mutant), Colo205 (ATCC accession number CCL-222; KRAS wild-type; BRAF mutant), WiDr (ATCC accession number CCL-218; KRAS wild-type; BRAF mutant) and HT-29 (ATCC accession number HTB-38; KRAS wild-type; BRAF mutant). These cell lines are known to carry mutations in their KRAS or BRAF genes ((Seth, Crook et al. 2009); (Davies, Logie et al. 2007)).

Humanised SC104 Antibody has Potent Killing Activity Against Human Colon Tumour Cells Carrying Mutations in KRAS or BRAF Genes

Humanised SC104 antibody (SEQ ID NO:7/SEQ ID NO:50), but not the human isotype control, had potent antibody-dependent cell-mediated cytotoxicity against a panel of human colon cancer cell lines carrying KRAS or BRAF mutations using peripheral blood mononuclear cells of normal human donors. FIG. 5 depicts the killing of cell line DLD-1 known to carry mutated KRAS but wild-type BRAF genes. FIG. 6 depicts the killing of cell lines Colo201, Colo205, WiDr and HT-29 known to carry mutated BRAF but wild-type KRAS genes. Similar results were obtained using these cell lines and peripheral blood mononuclear cells derived from other human donors. ADCC function was measured as described in Example 2

Example 5 Effector Function Enhancement of SC104 Antibodies

Effector function of antibodies can be enhanced by increasing antibody-dependent cell-mediated cytotoxicity or complement-dependent-cytotoxicity or by the combination of antibody-dependent cell-mediated cytotoxicity and complement-dependent-cytotoxicity.

ADCC Enhancement

SC104 antibody variants and chimeric SC104 were engineered for enhanced antibody-dependent cell-mediated cytotoxicity (ADCC) activity using standard modifications to the Fc region of the antibody. Standard methods include for example protein-engineering or glyco-engineering of the Fc region of the antibody.

As an example of glyco-engineering, CHO cells producing humanised SC104 antibody variants or chimeric SC104 antibody were incubated for 8 to 10 days with kifunensin (0.25 μg/ml) according to Zhou et al. (Zhou, Shankara et al. 2008). Subsequently antibody was purified, and ADCC function was measured as described in Example 2.

As an example of protein-engineering, mutations in the constant heavy chain sequences were generated as described by Lazar et al., 2006 (Lazar, Dang et al. 2006). Specifically, S122D, S181A, I215E mutations were introduced into the Fc sequence SEQ ID NO:52, to form SEQ ID NO:53. A number of humanised antibodies along with the chimeric antibody possessing the enhanced Fc-region SEQ ID NO:53 were tested in ADCC assays following their expression in CHO cells and purification by protein A chromatography. ADCC function was measured as described in Example 2.

Another example of glyco-engineering used the Potelligent® method as described in Shinkawa T. et al., 2003 (J Biol Chem 278: 3466-73). The variable light and heavy chain regions of the humanised antibody variants were expressed as an IgG1 on a standard constant region backbone. The sequence of the constant heavy chain was GenBank P01857.1 and the sequence of the constant light chain was NCBI accession number P01834. ADCC function was measured as described in Example 2.

Effector Enhanced SC104 Humanised Antibody Variants and Chimeric Sc104 Antibody have increased antibody-dependent cell-mediated cytotoxicity

In a series of experiments protein-engineering or glyco-engineering was applied to increase antibody-dependent cell-mediated cytotoxicity of chimeric SC104 antibody and SC104 humanised antibody variants. Compared with the unmodified antibodies, the Fc-engineered (SEQ ID NO:53) or kifunensin-treated SC104 humanised antibody variants and chimeric SC104 antibody showed increased antibody-dependent cell-mediated cytotoxicity against Colo205 tumour cells. FIG. 7 shows an example for markedly increased killing of human colon cancer cell WiDr (ATCC accession number CCL-218) by kifunensin-treated humanised SC104 antibody (SEQ ID NO:7/SEQ ID NO:50).

Example 6 Mouse Xenograft Tumour Model

Female BALB/c nude mice were inoculated subcutaneously with 2×10⁶ human colon cancer HT-29 cells (ATCC accession number HTB-38). On the same day as tumour cell inoculation (day 0), mice were randomised based on body weight into two treatment groups (n=10 per group). Each group was treated intraperitoneally with either the vehicle control (PBS, 10 ml/kg) or humanised SC104 antibody (10 mg/kg). The vehicle control and humanised SC104 antibody were administered twice weekly for four weeks. Tumour volume was calculated three times weekly using the following formula: Volume (mm³)=length×diameter²×π/6.

During the course of the study some mice had to be culled due to excessive body weight loss resulting in reduced mouse numbers for vehicle control (n=6) and antibody (n=9) treatment groups. Upon termination of the study (day 27), tumours were excised post-mortem from all mice, cleaned of skin and weighed.

Potent Anti-Tumour Efficacy of Humanised SC104 Antibody In Vivo

Treatment of tumour-bearing mice with humanised SC104 antibody (SEQ ID NO:7/SEQ ID NO:50) resulted in significant, reduced tumour volume and tumour weight compared with vehicle control treatment (FIG. 8). One can envisage that humanised SC104 antibody variants are useful for the treatment of colorectal cancers in humans either as mono-therapy or in combination with other therapeutic anti-tumour agents, for example chemotherapy, small molecules or biologics. The in vivo efficacy of such combination therapies could be evaluated in mouse tumour xenograft models.

Example 7 Competition Assay

SC104 antigen-positive colon cancer cells (Colo205; formaldehyde fixed cells) were incubated at various concentrations with competitor antibody (humanised SC104 variant SEQ ID NO:7/SEQ ID NO:50 or control human IgG1 isotype) followed by incubation with a fixed concentration (1 ug/ml, upper panel; 10 ug/ml, lower panel) of FITC-conjugated mouse SC104 antibody; subsequent signal analysis was performed by flow cytometry analysis.

As shown in FIG. 9 incubation with competitor antibody specifically decreased binding of mouse SC104 in a dose dependent fashion (vs incubation with control isotype antibody); at equal concentration levels of mouse and competitor antibodies, binding of mouse SC104 was reduced by ˜23% (upper panel) or ˜32% (lower panel) compared with isotype control antibody. Each point represents mean±SD of three replicate samples.

TABLE 1 CDR sequences of SC104 Variable region CDR number CDR Sequence V_(H) 1 SGYSWH (Kabat) GYSITSGYSWH (AbM) V_(H) 2 HIHFSGRPTYNPSLSS V_(H) 3 KGKGSDDGLNY V_(L) 1 SASSSLSYIH V_(L) 2 DTSNLAS V_(L) 3 FQGSEYPLT

TABLE 2 Humanised SC104 antibody binds to various human tumour types Percentage of membranous immunostaining Tumour type n Negative Weak Moderate Strong Colon 41 31.7 17.1 4.9 46.3 Colon adenoma, low 39 25.6 7.7 28.2 38.5 grade Colon adenoma, high 30 33.3 6.7 13.3 46.7 grade Stomach, diffuse 36 22.2 2.8 13.9 61.1 Stomach, intestinal 35 45.7 5.7 2.9 45.7 Gall bladder carcinoma 22 31.8 4.5 4.5 59.1 Small intestine 13 61.5 23.1 7.7 7.7 carcinoma Esophageal carcinoma, 47 59.6 4.3 4.3 31.9 adeno Esophageal carcinoma, 47 87.2 4.3 2.1 6.4 SQCC Rectal carcinoma 10 70.0 30.0 0 0 Gastrointestinal stroma 44 100.0 0 0 0 (GIST) Lung - NSCLC 8 37.5 37.5 12.5 12.5 Lung - SQCC 55 63.6 10.9 21.8 3.6 Lung - bronchoalveolar 13 61.5 15.4 0 23.1 Pancreas - ductal 43 14.0 2.3 4.7 79.1 adenocarcinoma Pancreas - papillary 20 5.0 0 0 95.0 adenocarcinoma Endometrium - 58 25.9 10.3 12.1 51.7 endometrioid Endometrium - serous 50 48.0 16.0 14.0 22.0 Ovarian - endometrioid 21 38.1 19.0 19.0 23.8 Ovarian - mucinous 41 51.2 2.4 2.4 43.9 Cervical - adeno 36 41.7 22.2 5.6 30.6 Urinary bladder - non- 56 30.4 16.1 25.0 28.6 invasive Warthin's tumour 48 8.3 12.5 14.6 64.6

TABLE 3 Humanised SC104 antibody variants demonstrate potent antibody-dependent cell- mediated-cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) activities Direct SC104 V_(L) (SEQ ID NO)/ Binding killing ADCC CDC antibody form V_(H) (SEQ ID NO) C170 Colo205 C170 C170 Colo205 Colo205 chimeric SEQ ID NO: 4/ 100 100 100 100 100 100 SEQ ID NO: 2 humanised SEQ ID NO: 7/ 101.4 104.8 98.9 154.2 120.3 54.1 SEQ ID NO: 25 humanised SEQ ID NO: 7/ 106.8 112.0 89.4 162.5 203.5 136.0 SEQ ID NO: 50 humanised SEQ ID NO: 8/ 99.0 95.8 48.7 32.3 84.4 9.9 SEQ ID NO: 26 humanised SEQ ID NO: 8/ 103.5 104.3 50.3 47.3 nd 20.1 SEQ ID NO: 38 expressed as percentage activity relative to chimeric SC104; nd, not determined; when tested similar data were obtained in other experiments

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SUMMARY OF SEQUENCE LISTING

-   SEQ ID NO:1: Amino acid sequence of murine SC104 heavy chain     variable region. -   SEQ ID NO:2: Amino acid sequence of chimeric SC104 heavy chain with     mouse variable region and human IgG1 backbone (human IgG1 heavy     chain CH1, hinge, CH2 & CH3 domains). -   SEQ ID NO:3: Amino acid sequence of murine SC104 light chain     variable region. -   SEQ ID NO:4: Amino acid sequence of chimeric SC104 light chain with     mouse variable region and human light chain constant region. -   SEQ ID NO:5: Heavy chain signal sequence. -   SEQ ID NO:6: Light chain signal sequence. -   SEQ ID NO:7: 1U6A-based SC104 light chain polypeptide sequence     incorporating substitution A15P. -   SEQ ID NO:8: 1QLR-based SC104 light chain. -   SEQ ID NO:9: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence. -   SEQ ID NO:10: Kabat-grafted 1QLR-based SC104 heavy chain polypeptide     sequence. -   SEQ ID NO:11: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1U6A-based SC104 heavy chain polypeptide sequence. -   SEQ ID NO:12: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     I QLR-based SC104 heavy chain polypeptide sequence. -   SEQ ID NO:13: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1U6A-based SC104 heavy chain polypeptide sequence incorporating six     substitutions. -   SEQ ID NO:14: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1U6A-based SC104 heavy chain polypeptide sequence incorporating     eight substitutions. -   SEQ ID NO:15: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating six substitutions. -   SEQ ID NO:16: 1U6A-based SC104 light chain polypeptide sequence     incorporating three substitutions. -   SEQ ID NO:17: Kabat-grafted 1 QLR-based SC104 heavy chain     polypeptide sequence incorporating four substitutions. -   SEQ ID NO:18: 1QLR-based SC104 light chain polypeptide sequence     incorporating three substitutions. -   SEQ ID NO:19: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1U6A-based SC104 heavy chain polypeptide sequence incorporating     substitutions Q1E and Q46E. -   SEQ ID NO:20: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1U6A-based SC104 heavy chain polypeptide sequence incorporating     substitutions Q1E and 148M. -   SEQ ID NO:21: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1U6A-based SC104 heavy chain polypeptide sequence incorporating     substitutions Q1E and V671. -   SEQ ID NO:22: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1U6A-based SC104 heavy chain polypeptide sequence incorporating     substitutions Q1E and T68S. -   SEQ ID NO:23: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1U6A-based SC104 heavy chain polypeptide sequence incorporating     substitutions Q1E and V71R. -   SEQ ID NO:24: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1U6A-based SC104 heavy chain polypeptide sequence incorporating     substitutions Q1E and E72D. -   SEQ ID NO:25: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1U6A-based SC104 heavy chain polypeptide sequence incorporating     substitution V71R. -   SEQ ID NO:26: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1 QLR-based SC104 heavy chain polypeptide sequence incorporating     substitution V71R. -   SEQ ID NO:27: Kabat-grafted 1 QLR-based SC104 heavy chain     polypeptide sequence incorporating substitution V71R. -   SEQ ID NO:28: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitution V71R. -   SEQ ID NO:29: Kabat-grafted 1 QLR-based SC104 heavy chain     polypeptide sequence incorporating substitutions G27Y and V71R. -   SEQ ID NO:30: Amino acid sequence of chimeric SC104 heavy chain with     mouse variable region and human IgG1 backbone (human IgG1 heavy     chain CH1, hinge, CH2 & CH3 domains) incorporating CDR-H2     substitution F53W. -   SEQ ID NO:31: Amino acid sequence of chimeric SC104 heavy chain with     mouse variable region and human IgG1 backbone (human IgG1 heavy     chain CH1, hinge, CH2 & CH3 domains) incorporating CDR-H2     substitution F53Y. -   SEQ ID NO:32: Amino acid sequence of chimeric SC104 heavy chain with     mouse variable region and human IgG1 backbone (human IgG1 heavy     chain CH1, hinge, CH2 & CH3 domains) incorporating CDR-H2     substitution F53P. -   SEQ ID NO:33: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1QLR-based SC104 heavy chain polypeptide sequence incorporating     substitutions S64K and V71R. -   SEQ ID NO:34: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1 QLR-based SC104 heavy chain polypeptide sequence -   SEQ ID NO:35: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1 QLR-based SC104 heavy chain polypeptide sequence incorporating     substitutions S64H and V71R. -   SEQ ID NO:36: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1QLR-based SC104 heavy chain polypeptide sequence incorporating     substitutions S64F and V71R. -   SEQ ID NO:37: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1QLR-based SC104 heavy chain polypeptide sequence incorporating     substitutions S64R and V71R. -   SEQ ID NO:38: Kabat-grafted 1 QLR-based SC104 heavy chain     polypeptide sequence incorporating substitutions G27Y, F29I, T30S,     S64K and V71R. -   SEQ ID NO:39: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1U6A-based SC104 heavy chain polypeptide sequence incorporating     substitutions S64K and V71R. -   SEQ ID NO:40: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1U6A-based SC104 heavy chain polypeptide sequence incorporating     substitutions S64L and V71R. -   SEQ ID NO:41: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1U6A-based SC104 heavy chain polypeptide sequence incorporating     substitutions S64H and V71R. -   SEQ ID NO:42: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1U6A-based SC104 heavy chain polypeptide sequence incorporating     substitutions S64F and V71R. -   SEQ ID NO:43: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1U6A-based SC104 heavy chain polypeptide sequence incorporating     substitutions S64R and V71R. -   SEQ ID NO:44: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1U6A-based SC104 heavy chain polypeptide sequence -   SEQ ID NO:45: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1U6A-based SC104 heavy chain polypeptide sequence incorporating     substitutions S40P, S64K and V71R. -   SEQ ID NO:46: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1U6A-based SC104 heavy chain polypeptide sequence incorporating     substitutions S40P, S64L and V71R. -   SEQ ID NO:47: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1U6A-based SC104 heavy chain polypeptide sequence incorporating     substitutions S40P, S64H and V71R. -   SEQ ID NO:48: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1U6A-based SC104 heavy chain polypeptide sequence incorporating     substitutions S40P, S64F and V71R. -   SEQ ID NO:49: AbM-grafted CDR-H1, Kabat-defined CDR-H2 and CDR-H3 of     1U6A-based SC104 heavy chain polypeptide sequence incorporating     substitutions S40P, S64R and V71R. -   SEQ ID NO:50: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, T30S, S40P, S64K and     V71R. -   SEQ ID NO:51: Amino acid sequence of chimeric SC104 heavy chain with     mouse variable region and human IgG1 backbone (human IgG1 heavy     chain CH1, hinge, CH2 & CH3 domains) incorporating substitution     N60D. -   SEQ ID NO:52: Heavy chain constant region incorporating hinge, CH1,     CH2 and CH3 domains. -   SEQ ID NO:53: Heavy chain constant region incorporating hinge, CH1,     CH2 and CH3 domains, incorporating amino acid substitutions S122D,     S181A, I215E. -   SEQ ID NO:54: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, I29A, T30S, -   SEQ ID NO:55: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, I29C, T30S, S40P, S64K     and V71R. -   SEQ ID NO:56: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, I29D, T30S, S40P, S64K     and V71R. -   SEQ ID NO:57: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, I29E, T30S, S40P, S64K     and V71R. -   SEQ ID NO:58: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, I29F, T30S, S40P, S64K     and V71R. -   SEQ ID NO:59: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, I29G, T30S, S40P, S64K     and V71R. -   SEQ ID NO:60: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, I29H, T30S, S40P, S64K     and V71R. -   SEQ ID NO:61: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, I29K, T30S, S40P, S64K     and V71R. -   SEQ ID NO:62: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, I29L, T30S, S40P, S64K     and V71R. -   SEQ ID NO:63: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, I29M, T30S, S40P, S64K     and V71R. -   SEQ ID NO:64: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, I29N, T30S, S40P, S64K     and V71R. -   SEQ ID NO:65: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, I29P, T30S, S40P, S64K     and V71R. -   SEQ ID NO:66: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, I29Q, T30S, S40P, S64K     and V71R. -   SEQ ID NO:67: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, I29R, T30S, S40P, S64K     and V71R. -   SEQ ID NO:68: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, I29S, T30S, S40P, S64K     and V71R. -   SEQ ID NO:69: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, I29T, T30S, S40P, S64K     and V71R. -   SEQ ID NO:70: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, I29V, T30S, S40P, S64K     and V71R. -   SEQ ID NO:71: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, I29W, T30S, S40P, S64K     and V71R. -   SEQ ID NO:72: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, I29Y, T30S, S40P, S64K     and V71R. -   SEQ ID NO:73: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, T30S, S40P, S64K and     V71A. -   SEQ ID NO:74: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, T30S, S40P, S64K and     V71C. -   SEQ ID NO:75: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, T30S, S40P, S64K and     V71D. -   SEQ ID NO:76: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, T30S, S40P, S64K and     V71E. -   SEQ ID NO:77: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, T30S, S40P, S64K and     V71F. -   SEQ ID NO:78: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, T30S, S40P, S64K and     V71G. -   SEQ ID NO:79: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, T30S, S40P, S64K and     V71H. -   SEQ ID NO:80: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, T30S, S40P, S64K and     V71I. -   SEQ ID NO:81: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, T30S, S40P, S64K and     V71K. -   SEQ ID NO:82: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, T30S, S40P, S64K and     V71L. -   SEQ ID NO:83: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, T30S, S40P, S64K and     V71M. -   SEQ ID NO:84: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, T30S, S40P, S64K and     V71N. -   SEQ ID NO:85: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, T30S, S40P, S64K and     V71P. -   SEQ ID NO:86: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, T30S, S40P, S64K and     V71Q. -   SEQ ID NO:87: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, T30S, S40P, S64K and     V71S. -   SEQ ID NO:88: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, T30S, S40P, S64K and     V71T. -   SEQ ID NO:89: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, T30S, S40P, S64K and     V71V. -   SEQ ID NO:90: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, T30S, S40P, S64K and     V71W. -   SEQ ID NO:91: Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, T30S, S40P, S64K and     V71Y. -   SEQ ID NO:92: Heavy chain constant region incorporating hinge, CH1,     CH2 and CH3 domains. -   SEQ ID NO:93 Light chain constant domain -   SEQ ID NO:94 Kabat-grafted 1U6A-based SC104 heavy chain polypeptide     sequence incorporating substitutions G27Y, T30S, S40P, S64K and V71R 

1. A method of treating cancer in a subject wherein the cancer comprises mutated KRAS or BRAF genes, the method comprising administering to the subject an effective amount of an antibody or antigen binding fragment thereof wherein the antibody or antigen binding fragment thereof competes with SC104 for binding to the human colon cancer cell line Colo205.
 2. A method of treating cancer in a subject, the method comprising testing the cancer for the presence of mutated KRAS or BRAF genes and administering to subjects in which the cancer comprises mutated KRAS or BRAF genes an effective amount of an antibody or antigen binding fragment thereof wherein the antibody or antigen binding fragment thereof competes with SC104 for binding to the human colon cancer cell line Colo205.
 3. A method as claimed in claim 1, wherein the cancer is selected from the group consisting of colon cancer, pancreatic cancer, and gastric cancer.
 4. A method as claimed in claim 1, wherein the antibody is an SC104 chimera.
 5. A method as claimed in claim 1, wherein the antibody is a human-mouse chimera.
 6. A method as claimed in claim 1, wherein the antibody is a deimmunized SC104 antibody or antigen binding fragment thereof.
 7. A method as claimed in claim 1 wherein the antibody is a humanized SC104 antibody or antigen binding fragment thereof.
 8. A method as claimed in claim 1, wherein the antibody or antigen binding fragment comprises at least one sequence selected from the group consisting of SEQ ID NO:7, SEQ ID NO:8, SEQ ID NO:11, SEQ ID NO:12, SEQ ID NO:13, SEQ ID NO:14, SEQ ID NO:15, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:19, SEQ ID NO:20, SEQ ID NO:21, SEQ ID NO:22, SEQ ID NO:23, SEQ ID NO:24, SEQ ID NO:25, SEQ ID NO:26, SEQ ID NO:27, SEQ ID NO:28, SEQ ID NO:29, SEQ ID NO:30, SEQ ID NO:31, SEQ ID NO:32, SEQ ID NO:33, SEQ ID NO:34, SEQ ID NO:35, SEQ ID NO:36, SEQ ID NO:37, SEQ ID NO:38, SEQ ID NO:39, SEQ ID NO:40, SEQ ID NO:41, SEQ ID NO:42, SEQ ID NO:43, SEQ ID NO:44, SEQ ID NO:45, SEQ ID NO:46, SEQ ID NO:47, SEQ ID NO:48, SEQ ID NO:49, SEQ ID NO:50, SEQ ID NO:51, SEQ ID NO:52, SEQ ID NO:53, SEQ ID NO:62, SEQ ID NO:69, SEQ ID NO:70, SEQ ID NO:73, SEQ ID NO:74, SEQ ID NO:75, SEQ ID NO:76, SEQ ID NO:77, SEQ ID NO:78, SEQ ID NO:79, SEQ ID NO:80, SEQ ID NO:81, SEQ ID NO:82, SEQ ID NO:83, SEQ ID NO:84, SEQ ID NO:85, SEQ ID NO:86, SEQ ID NO:87, SEQ ID NO:88, SEQ ID NO:89, SEQ ID NO:90, SEQ ID NO:91, and SEQ ID NO:94.
 9. A method as claimed in claim 1, wherein the antibody or antigen binding fragment comprises light and heavy chain combinations selected from the group consisting of SEQ ID NO:7/SEQ ID NO:25, SEQ ID NO:7/SEQ ID NO:50, SEQ ID NO:7/SEQ ID NO:94, SEQ ID NO:8/SEQ ID NO:26 and SEQ ID NO:8/SEQ ID NO:38. 10-13. (canceled)
 14. The method as claimed in claim 1, wherein the antibody that competes with SC104 or antigen binding fragment thereof has been glyco-engineered to enhance antibody-dependent cell-mediated cytotoxicity.
 15. A method as claimed in claim 2, wherein the cancer is selected from the group consisting of colon cancer, pancreatic cancer, and gastric cancer.
 16. A method as claimed in claim 2, wherein the antibody is an SC104 chimera.
 17. A method as claimed in claim 2, wherein the antibody is a human-mouse chimera.
 18. A method as claimed in claim 2, wherein the antibody is a deimmunized SC104 antibody or antigen binding fragment thereof.
 19. A method as claimed in claim 2, wherein the antibody is a humanized SC104 antibody or antigen binding fragment thereof.
 20. A method as claimed in claim 2, wherein the antibody or antigen binding fragment comprises at least one sequence selected from the group consisting of SEQ ID NO:7, SEQ ID NO:8, SEQ ID NO:11, SEQ ID NO:12, SEQ ID NO:13, SEQ ID NO:14, SEQ ID NO:15, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:19, SEQ ID NO:20, SEQ ID NO:21, SEQ ID NO:22, SEQ ID NO:23, SEQ ID NO:24, SEQ ID NO:25, SEQ ID NO:26, SEQ ID NO:27, SEQ ID NO:28, SEQ ID NO:29, SEQ ID NO:30, SEQ ID NO:31, SEQ ID NO:32, SEQ ID NO:33, SEQ ID NO:34, SEQ ID NO:35, SEQ ID NO:36, SEQ ID NO:37, SEQ ID NO:38, SEQ ID NO:39, SEQ ID NO:40, SEQ ID NO:41, SEQ ID NO:42, SEQ ID NO:43, SEQ ID NO:44, SEQ ID NO:45, SEQ ID NO:46, SEQ ID NO:47, SEQ ID NO:48, SEQ ID NO:49, SEQ ID NO:50, SEQ ID NO:51, SEQ ID NO:52, SEQ ID NO:53, SEQ ID NO:62, SEQ ID NO:69, SEQ ID NO:70, SEQ ID NO:73, SEQ ID NO:74, SEQ ID NO:75, SEQ ID NO:76, SEQ ID NO:77, SEQ ID NO:78, SEQ ID NO:79, SEQ ID NO:80, SEQ ID NO:81, SEQ ID NO:82, SEQ ID NO:83, SEQ ID NO:84, SEQ ID NO:85, SEQ ID NO:86, SEQ ID NO:87, SEQ ID NO:88, SEQ ID NO:89, SEQ ID NO:90, SEQ ID NO:91, and SEQ ID NO:94.
 21. A method as claimed in claim 2, wherein the antibody or antigen binding fragment comprises light and heavy chain combinations selected from the group consisting of SEQ ID NO:7/SEQ ID NO:25, SEQ ID NO:7/SEQ ID NO:50, SEQ ID NO:7/SEQ ID NO:94, SEQ ID NO:8/SEQ ID NO:26 and SEQ ID NO:8/SEQ ID NO:38.
 22. The method as claimed in claim 2, wherein the antibody that competes with SC104 or antigen binding fragment thereof has been glyco-engineered to enhance antibody-dependent cell-mediated cytotoxicity. 